脉冲法造型确能均匀地紧实任何高度和形状的模型周围的型砂,是由于此法提高了型砂的流动性。为了弄清这个现象的实质,将造型用砂看作由固态、液态和气态三种组分组成的介质。如认定型砂骨架和液态部分是不可压缩的,则可用型砂容积的变化来计算孔隙容积的改变。由于密闭空腔中型砂的变形发生在0.02～0.05秒内,孔隙容积的减小将引起处于型砂孔隙 The pulsating method does indeed compact the sand around the model of any height and shape uniformly because it improves the fluidity of the sand. In order to understand the essence of this phenomenon, the modeling sand is considered as a medium composed of three components, solid, liquid and gaseous. If the foundations of sand and liquid are not compressible, then the change in pore volume can be used to calculate the change in pore volume. Since the deformation of the closed sand in the closed cavity occurs within 0.02-0.05 seconds, the reduction of the volume of the pores will cause the pores in the sand